1. Field of the Invention
The present invention relates to a surface plate provided in a wafer double-side grinding device, and more particularly, to a surface plate of a wafer double-side grinding device for preventing slurry used in a double-side grinding process from being deposited on the surface plate, and a double-side grinding device including the same.
2. Description of the Related Art
In general, silicon wafers are manufactured through a slicing process in which a monocrystalline silicon ingot is sliced in a wafer shape, a lapping process in which the wafer is improved in flatness while being ground in a desired thickness, an etching process for removing a damage layer in the wafer, a polishing process for polishing a surface of the wafer to a mirror-like surface and improving flatness of the wafer, and a cleaning process for removing contaminants on the surface of the wafer.
To perform the lapping process on the wafer, a wafer carrier is disposed between an upper surface plate and a lower surface plate, and a wafer is disposed on the wafer carrier. Then, when the upper and lower surface plates rotate while continuously supplying slurry in which grinding particles, a dispersant, and a diluent, the surface of the wafer is ground by the grinding particles contained in the slurry. Generally, the main ingredients in abrasive materials are alumina or zirconia or silica. The abrasive material plays a major role in a double-side grinding process. Also, the dispersant is consist of a surfactant and amines. The dispersant may prevent re-aggregation between the particles of the abrasive material and precipitation of the particles of the abrasive material from occurring to allow the wafer to be smoothly ground.
Here, appropriate supply of the slurry that substantially grinds the wafer has significant effects on flatness of the wafer. Thus, a lattice-shaped groove for smoothly supplying and discharging the slurry is defined in a surface of each of the upper and lower surface plates to allow the slurry to be supplied and discharged therethrough.
The surface plate used in the practical lapping process has surfaces plate grooves that are spaced about 1 cm to about 4 cm apart from each other in transversal and longitudinal directions to allow the slurry to be easily discharged and supplied therethrough. However, since a bottom part of the surface plate groove parallelly defined in a horizontal direction, the slurry that is not discharged after being used in the wafer grinding process may be deposited in the surface plate groove in a sludge form. The accumulated sludge may interrupt the flow of the newly supplied slurry, and thus the particles for grinding the wafer may not smoothly circulate the wafer grinding device.
Due to the above-described limitation, to maintain a grinding force of the wafer double-side grinding device, a groove digging work for removing the sludge accumulated in the surface plate groove has to be performed regularly.
FIG. 1 is a view illustrating a shape of the surface plate groove and distribution of the slurry according to the related art. Referring to FIG. 1, in a cross-sectional view of a lower surface plate 12 according to the related art viewed from a lateral side, each of surface plate grooves 7 are defined in a predetermined depth. Also, since the slurry 5 is distributed in parallel with a bottom surface of the surface plate groove 7, the slurry 5 may not be easily distributed outside the lower surface plate 12. Also, when the slurry is deposited between the surface plate grooves 7, the wafer may be deteriorated in quality during the wafer double-side grinding process.